That was a lot of money spent on honey, so I'm going to see if I can get some kind of return on investment. At 7.75% ABV that's like a strong beer but too sweet for anyone to want to drink an entire pint. I still had about a pound of honey left over so I mixed it with some hot water (to lower the viscosity) and then mixed that into the bochet. A thick foam appeared at the surface immediately. Once it settled down I checked the gravity but the change was negligible. I sealed the lid and the airlock has been bubbling steadily for about 24 hours now. Perhaps I can step feed it until the ABV gets sufficiently high. I'm going to leave it alone to do its thing until the activity slows and then I'll measure the gravity again. It seems like opening the lid and stirring it can sometimes slow or stop CO2 production.
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bochet that won't start fermenting
- Thread starter duffrecords
- Start date
A couple things then, TAKE THE LID OFF, if taking the lid off stimulates it to activity it might not have enouh oxygen, take off the lid, stir the snot out of it and then stir it some more, I think you need to add some water to lower your gravity, if you had it at 1.178 it was way to high and you keep adding honey to it, more like you should aim to drop the gravity down to a more reasonable level like 1.095 so you yeast has a chance to finish fermenting. Good luck, WVMJ
Duff,
There is a concept that you may not be familiar with - sugar is toxic to yeast and high sugar content inhibits yeast. This is one major reason why honey is stable. This concept can be expressed in the form of Delle units (DU). The formula for DU is:
DU = %sugar (w/v) + (4.5 * ABV)
In your mead, with gravity of 1.120 you have sugar of more than 31% (if you take out the impact of alcohol it would be higher). With an ABV of about 8%, this formula means you have in excess of 67 DU. This is enough to inhibit yeast in a harsh environment (low pH, sulfites, CO2 pressure, etc.). Above about 90 you won't have fermentation at all.
So when you have a struggling fermentation, adding more and more honey usually does not get you the desired result.
This batch may very well have some unidentified yeast inhibitor, and often the best way to handle that is to dilute it, and/or gradually add it into another healthy fermentation that will allow the yeast to get the job done.
There is a concept that you may not be familiar with - sugar is toxic to yeast and high sugar content inhibits yeast. This is one major reason why honey is stable. This concept can be expressed in the form of Delle units (DU). The formula for DU is:
DU = %sugar (w/v) + (4.5 * ABV)
In your mead, with gravity of 1.120 you have sugar of more than 31% (if you take out the impact of alcohol it would be higher). With an ABV of about 8%, this formula means you have in excess of 67 DU. This is enough to inhibit yeast in a harsh environment (low pH, sulfites, CO2 pressure, etc.). Above about 90 you won't have fermentation at all.
So when you have a struggling fermentation, adding more and more honey usually does not get you the desired result.
This batch may very well have some unidentified yeast inhibitor, and often the best way to handle that is to dilute it, and/or gradually add it into another healthy fermentation that will allow the yeast to get the job done.
Well, it's gone from 1.178 to 1.110 (so 9% ABV) and the airlock is bubbling steadily. Does that Delle unit formula use the Balling or Brix scale or does that matter? I read that they "differ in their conversion from weight percentage to specific gravity in the fifth and sixth decimal places of the specific gravity scale." If so, the Delle units in my last post (according to my hydrometer, which uses Balling) would be 64.75 and today's measurement would be 67.
My girlfriend doesn't taste any aluminum in the bochet and her palette is highly acute, so I think we're safe from that.
My girlfriend doesn't taste any aluminum in the bochet and her palette is highly acute, so I think we're safe from that.
I'm going to be starting a bochet in the next few months, and this thread is a fascinating read. Lots of information packed in here. 
I hope your batch turns out well! Glad to hear it's starting to ferment a bit better for you.
Side question, is there such a thing as burning a bochet too much? I've seen different recipes where they barely caremalize the sugar at all, and others where you boil it until black smoke appears. Does this damage the honey at all?
I hope your batch turns out well! Glad to hear it's starting to ferment a bit better for you.
Side question, is there such a thing as burning a bochet too much? I've seen different recipes where they barely caremalize the sugar at all, and others where you boil it until black smoke appears. Does this damage the honey at all?
I think once you heat the honey. It is technically damaging it since your cooking some serious aromas, is it a bad thing for a bochet? Maybe not. My fear of the dark bochet has the color of spent motor oil but it tastes really nice, smooth, and complex. It's all in what you're going for.
Well, the fermentation seems to have come to a stop at 1.106, which makes it about 9.5% ABV. I'm going to dilute it and restart fermentation but I'm not sure how to calculate the ABV after that. Let's suppose I were to split it into two batches and add a gallon of water to each, lowering the specific gravity. How would I determine the ABV after it's been diluted?
Alternatively, I could transfer the entire 5 gallon batch to my 6.5 gallon primary and dilute it only marginally. Do you think that would be sufficient to bring the ABV above 12% or would I be better off splitting it in two where I'd have space to dilute it more aggressively?
Alternatively, I could transfer the entire 5 gallon batch to my 6.5 gallon primary and dilute it only marginally. Do you think that would be sufficient to bring the ABV above 12% or would I be better off splitting it in two where I'd have space to dilute it more aggressively?
It looks like you're at 70+ Delle units, so your yeast have done pretty well.
You can calculate the dilution using the following formula that works for blending:
(ABV¹*V¹) + (ABV²*V²) = (ABV³*V³)
ABV¹ is the ABV of the first batch.
ABV² is the ABV of the second batch. (which is zero if you are adding water)
V³ is the total volume (equal to V¹+V²)
So if you have a 5-gallon batch that you split in two, you have a V¹ of 2.5, and the the ABV¹ is 9.5%. If you add a gallon of water, the V² is 1 and the ABV² is zero so that term goes away. The V³ will be 3.5. So your ABV³ will be:
(9.5%*2.5) + (0*1) = (ABV³*3.5) so,
(9.5%*2.5)/3.5 = ABV³
6.8% = ABV³
If you use different dilution volumes you can plug them in and know where you'll be. This same methodology works for calculating the ABV effect of back sweetening, or topping up.
So if I wanted to calculate the resulting percent sugar after diluting, would that also work like this?
(sugar¹*V¹) + (sugar²*V²) = (sugar³*V³)
(sugar¹*V¹) + (sugar²*V²) = (sugar³*V³)
Yep, and if you get your volumes measured right, you'll be able to confirm with your hydrometer.
I made a spreadsheet that calculates the change in %sugar, ABV, and Delle units, and then their corresponding values if fermentation could (theoretically) complete to dryness. At first, that theoretical number goes above the current Delle units (67.82) but then after adding 0.9 gallons of water, it opens the door for further fermentation. I'd like this thing to be at least 12% ABV so it looks like I should add 2.5 gallons to allow that. Above that, it seems to roll off logarithmically, so I guess I can't expect much more than that.
I finally got some free time to split the batch into two 2.5 gallon batches, diluted by a gallon of water each. The hydrometer now reads 1.080 SG and 19.5% sugar (Balling). By the blending formula mentioned by Medsen Fey, the ABV should now be 6.8%, which brings the Delle units somewhere around 50.1. I prepared two starters of Red Star Premier Cuvee (since it yielded 18% in the hibiscus mead I just bottled). After 15 minutes of hydration, I added about 1.5 tablespoons of the partially-fermented bochet to each starter and agitated them. After about an hour, they both were producing a thick, foamy cap so I poured them into the primaries. The airlocks bubbled for a few minutes but this morning (about 12 hours later) they were still. The yeast might be in the lag phase. I unsealed the lids, hoping they will benefit from less pressure. Man, this has been my most difficult batch yet.
Fermentation seemed slow so on 5/26 I made two new Premier Cuvée starters and built them up incrementally over the course of a day, as Jack Keller's web site advises. At first, it created a big, foamy cap but the more must I added, the less visible the activity was. I pitched it on 5/27 and waited. SG on 5/23 was 1.080; now it is 1.070, so the yeast is doing something, even if the liquid is still. This was the same experience I had the last time I used Premier Cuvée on a mead. Hopefully, it will stealthily make its way up to 18% like that batch did.
When restarting a really challenging batch, it is common to see little activity and just a slow drop in gravity. I would suggest that you aerate it well, give it some yeast hulls, and try to keep the temp up to at least 70°F, then be very patient.
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I mixed 3.5 tsp of Yeastex into each primary and aerated them with an O2 tank and diffusion stone for about 30 seconds each. The foam gradually dissipated but by the next morning, a fine film of bubbles had appeared on the surface. Tonight I measured the SG delta of each buckets and added that to the initial 6.8% ABV (after dilution). They've reached 10% and 10.3%, respectively. Getting closer!
